1. Field of the Invention
The present invention relates to contents management technology. More particularly, the present invention relates to a method and an apparatus for efficiently managing digital contents to which a digital rights management (DRM) is applied.
2. Description of the Related Art
To protect paid contents being used in mobile devices from illegal copy or unauthorized redistribution, a digital rights management (DRM) technology has been proposed. To impose limitations on the usage of contents and thereby to effectively guarantee the right of copyright holders, the DRM applies an encryption technique to a variety of digital contents such as documents, music files, sound files, video files, e-books, and games. In general, the DRM provides a protective and administrable system for the whole process of creating, publishing, distributing, and consuming digital contents.
The contents to which DRM technology is applied (hereinafter referred to as ‘DRM contents’) always remain encrypted, thus allowing only authorized users the ability to access, decode and consume the encrypted contents. If such DRM content is illegally copied, unauthorized users who have no permission by a license typically fail to decrypt the encrypted content and are denied access. Therefore, the DRM technology can be useful to prevent illegal copying.
In operation, in DRM a license is created in a DRM server and then sold to a user who wishes to use/access the digital contents. Such a license to use contents is stored separately from digital contents in a user's device or player (hereinafter named generically ‘a mobile device’), thus permitting or restricting the usage of contents. Typically, a license may employ one or more numerous techniques to ensure that only the authorized user gains access to the content, for the amount of access agreed to, such as a count technique, an interval technique, a timed-count technique, an accumulation technique, and so forth.
A license contains information about limitations on the usage of DRM contents. For example, if a user purchases a certain MP3 music file with an exhaustible license that is available for ten plays, he or she can use the purchased music file just ten times. In this particular case, whenever that music file is played, the authorized count is reduced by one. If the count becomes finally zero by the tenth time the music is played (i.e., if a license expires), the music file cannot be accessed any longer. So a user who wants more use of the music file must renew their license, or obtain a license for a longer or shorter number of replays, as desired.
On the other hand, when receiving a request for playing a certain license-expired content, a conventional mobile device may display only a message that a play is not permissible, or may automatically jump to the next content.
In addition, a conventional mobile device may have in some non-DRM contents other than or in addition to DRM contents. Therefore, it may not be easy for a user to distinguish certain non-usable contents from usable contents in a content list which contains both DRM contents and non-DRM contents. This problem may become more critical as the quantity of content increases. Furthermore, it may be difficult to distinguish license-expired, non-usable DRM contents from usable DRM contents among DRM contents arranged in a content list. That is, there is no way of distinguishing DRM contents from a variety of contents, or distinguishing license-expired DRM contents from DRM contents. Accordingly, there often arises a user's inconvenience in managing contents as it may not be possible to ascertain the status of some of the contents.
Additionally, when licenses of certain DRM contents have expired, a user may repurchase some of licenses but may remove other contents instead. In this case, a user has to rely completely on his or her memory to remember whether to repurchase or remove each license of individual DRM contents. So, this inability to distinguish status also causes a user's inconvenience in managing contents.
Accordingly, there is a need in the art to allow an efficient management for different types of contents including DRM contents and normal contents.